Performance Of Cellular System Research Articles

Augmentation Opportunity of Transmission Control Protocol Performance in Wireless Networks and Cellular Systems

Augmentation Opportunity of Transmission Control Protocol Performance in Wireless Networks and Cellular Systems

Low-Complexity Energy-Efficient Resource Allocation for the Downlink of Cellular Systems

Energy efficiency (EE) is undoubtedly an important criterion for designing power-limited systems, and yet in a context of global energy saving, its relevance for power-unlimited systems is steadily growing. Equally, resource allocation is a well-known method for improving the performance of cellular systems. In this paper, we propose an EE optimization framework for the downlink of planar cellular systems over frequency-selective channels. Relying on this framework, we design two novel low-complexity resource allocation algorithms for the single-cell and coordinated multi-cell scenarios, which are EE-optimal and EE-suboptimal, respectively. We then utilize our algorithms for comparing the EE performance of the classic non-coordinated, orthogonal and coordinated multi-cell approaches in realistic power and system settings. Our results show that coordination can be a simple and effective method for improving the EE of cellular systems, especially for medium to large cell sizes. Indeed, by using a coordinated rather than a non-coordinated resource allocation approach, the per-sector energy consumption and transmit power can be reduced by up to 15% and more than 90%, respectively.

On the Performance of Cellular Two-Way Relay Systems with Analog Network Coding and Multiuser Diversity

We consider a cellular two-way relaying system in which a multi-antenna base station (BS) communicates bidirectionally with one of several single-antenna mobile stations (MSs) via a single-antenna relay using analog network coding. We employ MS selection coupled with beamforming at the BS so as to maximize the end-to-end signal-to-noise ratios. In the considered system, the target rates at the sources can generally be different owing to the asymmetric traffic flow in opposite directions. With such a general setup, we perform an overall system outage probability analysis over Rayleigh fading channels. For more insights, we derive a closed-form asymptotic expression for overall outage probability and an upper bound expression for ergodic sum-rate of the system. Based on these expressions, we show that the system achieves a performance gain, and a diversity order of minimum of the number of BS antennas and the number of MSs. Moreover, we address the problem of optimization of relay location in order to minimize the overall system outage under asymmetric traffic conditions. Finally, we provide numerical and simulation results to corroborate the theoretical analysis and the advantages offered by the proposed scheme.

Interaction of Frequency Allocation Schemes and Beam Forming on the Performance of Cellular Communication Systems Based on OFDM

In this study, the interaction of Beam Forming and frequency allocation schemes on an OFDM-based system such as LTE or WiMAX is investigated in order to support the maximum capacity and minimum outage probability. The results of simulation show that rank1 precode scheme based on MISO channel, according to what considered in LTE standard, along with the cell region division in order to allocate OFDM frequency carriers lead to a Considerable interest in the total capacity of the network in different traffics.

Multicell cooperative systems with multiple receive antennas

Multicell cooperation may play an important role in achieving high performance in cellular systems. Multicell cooperation with a single receive antenna at the mobile station has been widely investigated. Applying cooperation with multiple receive antennas, allowed in several emerging wireless standards, has met with some challenges. This is primarily because the transmit precoding/beamforming vector and receive processing have to be jointly optimized in multiple cells to combat out-of-cell interference. In this article, we first discuss the role of the receive antennas in a multicell environment, and then review recently proposed multicell cooperative algorithms and receive antenna techniques for different interference statistics. Finally, we highlight recent work on the fundamental limits of cooperation and the possibility of overcoming such limits by using multiple receive antennas in multicell cooperative networks.

Multicell cooperation [Guest Editorial

It is well recognized that the conventional cellular networks can no longer meet the user performance requirements in terms of throughput and coverage, which is due to the significant increase in the number of mobile users along with their traffic demands and the limited spectrum resource. This has stimulated the search for new approaches to alleviate this problem. Recently, cooperative communications at both the base station (BS) and mobile station (MS) levels has been proposed as a key technology to address this problem. Multicell cooperation is a new and emerging communication paradigm promising significant improvement in system capacity by mitigating intercell interference. It has been shown that, with the aid of multicell cooperation, a significant improvement of cellular system performance can be achieved, and the increase in throughput can be as large as an order of magnitude. Although the advantages of multicell cooperation have been demonstrated, many problems related to the research and development of practical and effective schemes for multicell cooperation exist. They have attracted considerable research attention in both academia and industry. This special issue of IEEE Wireless Communications puts together some recent results in the area of multicell cooperation for the next generation cellular wireless networks. It includes 11 articles, a brief account for each of which is provided below.

Average spectral efficiency of multi‐modulation cellular systems

Fourth generation systems are proposed to create extended wireless networks by applying frequency reuse techniques based on a cellular scheme. However, the total bandwidth needed depends on the channel bandwidth and the signal-to-interference protection ratio. The procedure to compute the performance of such interference-limited cellular systems is introduced in this study for systems with various modulation schemes (quadrature phase shift keying, 16 and 64 quadrature amplitude modulation), founding the percentage of the cell area that could be managed with each modulation, considering full load sectors. The conditions to share the same subcarriers between two users in next to base stations are also presented. The total bandwidth required to deploy a network with three sectored cells with 10 MHz channel results to be 360 MHz. This is a big issue since the size of the bands is generally 200 MHz, and it could limit the expected performance of these systems.

Multi-user transmitter preprocessing assisted uplink multi-cell multiple-input multiple-output system with base station cooperation over frequency-selective channels

The performance of cellular uplink multiple-input multiple-output systems, where co-channel interference (CCI) at the base stations (BSs) is a major performance impairment, is investigated in this correspondence principally from a multi-user transmitter preprocessing (MUTP) perspective over correlated frequency-selective channels. Transmitter preprocessing at the mobile station is formulated by singular value decomposition (SVD) of only the individual user’s channel state information (CSI) while post-processing exploits all the users’ CSI using BS cooperation. Our simulations show that this approach completely removes CCI and also outperforms classical zero-forcing multi-user detection, which has about the same detection complexity. Further, the results show that our system, coupled with the optimal ‘water-filling’ strategy for power allocation, results in higher capacity than the maximum signal-to-noise ratio strategy. Furthermore, SVD-based MUTP outperforms dirty paper coding and Tomlinson–Harashima precoding in terms of achievable symbol error rate.

English

In an environment with fluctuating demand and unpredictable parts mix compositions, the efficiency of cellular systems necessitates the use of virtual cells. Virtual cellular manufacturing systems (VCMSs) are based on a highly flexible manufacturing concept designed to improve the performance of classical cellular manufacturing systems (CMSs) and job shop manufacturing environment by creating virtual grouping the resources temporarily in the production planning and control system. The underlying concept is particularly valuable during high demands variety and variability and with increase in machines types required by parts for processing. Whereas researches on VCMSs are still in a preliminary stage, this concept has gained momentum during the last decade and a wide and diverse variety of solution techniques have been applied for solving part-machine cell formation problems in these systems. The aim of this paper is to provide a review on recent efforts and developments in the VCMSs area to make required comparisons among the published works and determine future research issues and high-impact research scopes to search more. In this study, the overview was on various criteria in detail. While already a few researchers tended to make surveys over VCMSs, some important criteria were neglected to review and consider, which this paper tried to cover them as a complementary and an updated version.   Key words: Cell formation, survey, virtual cellular manufacturing system.

Performance of multi-user transmitter preprocessing assisted MIMO system over correlated frequency-selective channels

In this contribution we present the performance of a multi-user transmitter preprocessing (MUTP) assisted multiple-input multiple-output (MIMO) space division multiple access (SDMA) system, aided by double space time transmit diversity (DSTTD) and space time block code (STBC) processing for downlink (DL) and uplink (UL) transmissions respectively. The MUTP is invoked by singular value decomposition (SVD) which exploits the channel state information (CSI) of all the users at the base station (BS) and only an individual user’s CSI at the mobile station (MS). Specifically, in this contribution, we investigate the performance of multi-user MIMO cellular systems in frequency-selective channels from a transmitter signal processing perspective, where multiple access interference (MAI) is the dominant channel impairment. In particular, the effects of three types of delay spread distributions on MUTP assisted MIMO SDMA systems pertaining to the Long Term Evolution (LTE) channel model are analyzed. The simulation results demonstrate that MUTP can perfectly eliminate MAI in addition to obviating the need for complex multi-user detectors (MUDs) both at the BS and MS. Further, SVD-based MUTP results in better achievable symbol error rate (SER) compared to popularly known precoding schemes such as block diagonalization (BD), dirty paper coding (DPC), Tomlinson–Harashima precoding (THP) and geometric mean decomposition (GMD). Furthermore, when turbo coding is invoked, coded SVD aided MUTP results in better achievable SER than an uncoded system.

CoMP clustering and backhaul limitations in cooperative cellular mobile access networks

Coordinated Multi-Point (CoMP) transmission and reception is a promising solution for managing interference and increasing performance in future wireless cellular systems. Due to its strict requirements in terms of capacity, latency, and synchronization among cooperating Base Stations (BSs), its successful deployment depends on the capability of the mobile backhaul network infrastructure.We deal with the feasibility of CoMP transmission/reception, in particular of Joint Transmission (JT). For this, we first evaluate which cluster sizes are reasonable from the wireless point-of-view to achieve the desired performance gains. Thereafter, we analyze how different backhaul topologies (e.g., mesh and tree structures) and backhaul network technologies (e.g., layer-2 switching and single-copy multicast capabilities) can support these desired clusters. We study for different traffic scenarios and backhaul connectivity levels, which part of the desired BS clusters are actually feasible according to the backhaul characteristics. We found out that a significant mismatch exists between the desired and feasible clusters. Neglecting this mismatch causes overheads in real JT implementations, which complicates or even prevents their deployment.Based on our findings, we propose a clustering system architecture that not only includes wireless information, as done in the state of the art, but also combines wireless and backhaul network feasibility information in a smart way. This avoids unnecessary signaling and User Equipment (UE) data exchange among BSs which are not eligible to take part in the cooperative cluster. Evaluations show that our scheme reduces the signaling and UE data exchange overhead by up to 85% compared to conventional clustering approaches, which do not take into account the backhaul network’s status.

Achieving the Maximum Sum Rate Using D.C. Programming in Cellular Networks

Intercell interference is the major limitation to the performance of future cellular systems. Despite the joint detection and joint transmission techniques aiming at interference cancellation which suffer from the limited possible cooperation among the nodes, power allocation is a promising approach for optimizing the system performance. If the interference is treated as noise, the power allocation optimization problem aiming at maximizing the sum rate with a total power constraint is nonconvex and up to now an open problem. In the present paper, the solution is found by reformulating the nonconvex objective function of the sum rate as a difference of two concave functions. A globally optimum power allocation is found by applying a branch-and-bound algorithm to the new formulation. In principle, the algorithm partitions the feasible region recursively into subregions where for every subregion the objective function is upper and lower bounded. For each subregion, a linear program is applied for estimating the upper bound of the sum rate which is derived from a convex maximization formulation of the problem with piecewise linearly approximated constraints. The performance is investigated by system-level simulations. The results show that the proposed algorithm outperforms the known conventional suboptimum schemes. Furthermore, it is shown that the algorithm asymptotically converges to a globally optimum power allocation.

Effects of Nakagami-Fading Parameters and Power Control Error on Performance of DS-CDMA Cellular Systems with Adaptive Beamforming

It is well known that power control error (PCE) is a critical issue in CDMA cellular systems. In this paper, the bit error rate (BER) of a direct sequence-code division multiple access (DS-CDMA) re...

Improved Resource Allocation Scheme in LTE Femtocell Systems based on Fractional Frequency Reuse

Femtocells provide high quality indoor communications with low transmit power. However, when femtocells are applied in cellular systems, a co-channel interference problem between macrocells and femtocells occurs because femtocells use the same spectrum as do the macrocells. To solve the co-channel interference problem, a previous study suggested a resource allocation scheme in LTE cellular systems using FFR. However, this conventional resource allocation scheme still has interference problems between macrocells and femtocells near the boundary of the sub-areas. In this paper, we define an optimization problem for resource allocation to femtocells and propose a femtocell resource allocation scheme to solve the optimization problem and the interference problems of the conventional scheme. The evaluation of the proposed scheme is conducted by System Level Simulation while varying the simulation environments. The simulation results show that the proposed scheme is superior to the conventional scheme and that it improves the overall performance of cellular systems.

Virtual cellular manufacturing system based on resource element approach and analyzing its performance over different basic layouts

Article history: Received 25 Feb 2010 Received in revised form June, 5, 2011 Accepted 7 July 2011 Available online 9 July 2011 This research aims to present how choosing a suitable layout can improve the performance of virtual cellular manufacturing systems (VCMSs), especially minimizing the material flow between machines required by each family group. To present the efficacy of basic layouts on performances of VCMSs, a multi-objective mathematical model with a goal programming (GP) approach is developed to generate VCMSs based on resource-elements (REs). The formulated model is coded in Lingo software and is run over functional and distributed arrangements of the same machines. The performance and the validity of the developed model are checked by a numerical example taken from the literature. The objective function of the mathematical model is measured for that example over two mentioned layout to compare the performance of the generated systems. Moreover, because of the material handling costs importance, material flows are measured to find the best option as a basic layout for VCMSs. To compare the performance of the generated system with the classical cellular manufacturing system (CMS), cell capacity utilization (CCU) is employed as an independent criterion to evaluate each system. The result illustrates the priority of distributed layouts for generating RE-based VCMSs because of its flexibility, minimizing the objective function for the mathematical model, and smaller material flow by the components. In addition, the generated VCMSs outperforms the classical CMS from the CCU point of view. © 2012 Growing Science Ltd. All rights reserved

WCDMA Uplink Load Estimation With Generalized Rake Receivers

A generalized rake (G-rake) receiver creates link gains by interference suppression. To fully exploit these gains for the enhancement of cellular system performance, the scheduler of a wideband code-division multiple-access (WCDMA) radio base station needs estimates of the uplink load after G-rake processing. This paper, therefore, proposes algorithms that estimate this load with a bandwidth as high as the channel estimation bandwidth. Link simulations support the obtained results.

System-level simulation methodology and platform for mobile cellular systems

System-level simulation has been widely used to evaluate the comprehensive performance of different mobile cellular systems. System-level simulation methodologies for different systems have been discussed by different organizations and institutions. However, the framework for a unified simulation methodology and platform has not been established. In this article, we propose a general unified simulation methodology for different cellular systems. Both the design of the simulation structure and the establishment of the simulation platform are studied. Meanwhile, the unified modeling and the realization of various modules related to the system-level simulation are presented. The proposed unified simulation methodology and the general simulation platform can be used to evaluate the performance of multiple mobile communication systems fairly. Finally, the overall performance of LTE and Mobile WiMAX systems is evaluated through the proposed framework. The key simulation results for both Full Buffer and VoIP traffics are presented and discussed. It is shown that the LTE system exhibits better performance than Mobile WiMAX.

User in the Loop: Mobility Aware Users Substantially Boost Spectral Efficiency of Cellular OFDMA Systems

Wireless cellular networks perform with a system spectral efficiency which depends on the user terminal distribution over the cell area. Due to the adaptive modulation and coding schemes used which depend on the signal-to-interference+noise (SINR) ratio, the achievable data rate is typically an order of magnitude higher in the cell center compared to the cell edge. The performance of IMT-Advanced cellular radio systems like IEEE 802.16m and 3GPP LTE-A will strongly depend on algorithms to cope with the low SINR in the service area. The new paradigm introduced in this paper motivates users to opportunistically change location according to operator recommendation displayed on the user terminal to achieve a much better SINR than currently available. Benefits are the increase of network capacity and higher data rates or potentially a financial incentive for the convinced users. Numeric results based on analysis of IMT scenarios are provided suggesting large cell spectral efficiency gains.

Achieving higher uplink performance and capacity via non-overlapping window adaptive maximum noise fraction beamforming technique

This study introduces a practical use of maximum noise fraction (MNF) in beamforming antennas that enhances users' uplink performance and capacity in cellular systems. The study introduces a non-overlapping window adaptive MNF technique. In addition, it mathematically analyses the proposed method. Moreover, the performance benefits created via MNF technique in uplink scenarios is also studied. A multi-carrier wideband code division multiple access (MC-WCDMA) system is used as a toy example to represent the benefits created by the proposed technique when it is used as a beamformer. The performance of the proposed technique for uplink MC-WCDMA is mathematically analysed. Simulations are conducted to study the performance and the capacity of the proposed method. The effect of the noise covariance matrix estimation that is vital for the operation of MNF systems on the performance is investigated.

Evaluation of cellular manufacturing configurations in dynamic conditions using simulation

This paper investigates the performance of classical cellular manufacturing systems compared to other two systems proposed in literature: fractal cells and remainder cells. This paper proposes three strategies to control a cellular manufacturing system with remainder cell and how to configure and control a fractal manufacturing system. The performance measures of the manufacturing systems are analyzed when several unforeseen events occur as: machine breakdowns, production mix changes, demand fluctuations, and processing time variability. A simulation environment developed by Arena® package was used to investigate the three manufacturing system configurations. The performance measures investigated are: throughput, throughput times of the parts, work in process, manufacturing utilization, and due date performance (tardiness). The simulation results show how the fractal and remainder cells can be a valid alternative to cellular manufacturing systems in a very dynamic environment.